OFDMA
Orthogonal frequency-division multiplexing (OFDM) is a modulation technique used at the physical layer (PHY) of a number of wireless networks, e.g., networks designed according to the well known IEEE 802.11a/g and IEEE 802.16/16e standards. Orthogonal Frequency-Division Multiple Access (OFDMA) is a multiple access scheme based on OFDM. In OFDMA, separate sets of orthogonal tones (sub-channels) and time slots are allocated to multiple transceivers (users or mobile stations) so that the transceivers can communicate concurrently. OFDMA is widely adopted in many next generation cellular networks such as 3GPP Long Term Evolution (LTE) and IEEE 802.16m due to its effectiveness and flexibility in radio resource allocation.
OFDMA Resource Allocation
The radio spectrum is a scarce resource in wireless communications, and therefore an efficient use of it is needed. The rapid growth of wireless applications and subscriber users have called for a good radio resource management (RRM) scheme that can increase the network capacity and, from a commercial point of view, save deployment cost. Consequently, developing an effective radio resource allocation scheme for OFDMA is of significant interest for industry.
The fundamental challenge in resource allocation is the inequality between the scarce spectrum that is available, and the vast area to be covered and large number of users to be served. In other words, the same frequency spectrum must be reused in multiple geographical areas or cells. This will inevitably incur inter-cell interference (ICI), when users or mobile stations (MSs) in neighboring cells use the same spectrum. In fact, ICI has been shown to be the predominant performance-limiting factor for wireless cellular networks. As a result, a significant amount of research has been devoted to developing ICI-aware radio resource allocation for cellular networks.